Revista de Biología Tropical ISSN: 0034-7744 [email protected] Universidad de Costa Rica Costa Rica

Benítez-Villalobos, Francisco; Abadia-Chanona, Quetzalli Yasú Densidad poblacional, distribución espacial y mortalidad natural del erizo de mar roseus (: ) en tres sitios de Oaxaca, México Revista de Biología Tropical, vol. 63, núm. 2, junio, 2015, pp. 121-133 Universidad de Costa Rica San Pedro de Montes de Oca, Costa Rica

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Abstract The Toxopneustes roseus is widely distributed along the east coast of the tropical Pacific, from Mexico to northern Peru. In our study we evaluated population features of this , such as population density, spatial distribution pattern and natural mortality, as well as the relationship between population density and several environmental variables. From October 2009 to September 2011 monthly sampling was carried out using belt transects in three localities of the coast of Oaxaca, Mexico: Estacahuite, Dos Hermanas and Isla Cacaluta. Additionally we recorded in situ temperature, salinity and pH in each locality. Records of irradiation and pluvial precipitation were obtained from databases. Distribution pattern of the urchins was characterized using the Morisita s Index and the models of Poisson s probability and Negative Binomial Distribution. Natural mortality was estimated using the modified method of Berry. A step by step analysis of Multiple Lineal Regression was applied to evaluate the relationship between population density and the recorded environmental variables. Mean (± SD) density was 0.12 ± 0.02 ind·m -2 (Estacahuite), 0.05 ± 0.01 ind·m -2 (Dos Hermanas) and 0.04 ± 0.01 ind·m -2 (Isla Cacaluta). The pat - tern of spatial distribution of T. roseus was aggregated in most of the sampled months in all the localities. In Estacahuite natural mortality was 0.45 and in Dos Hermanas it was 0.46, it was not possible to calculate mor - tality for Isla Cacaluta. Of the recorded environmental variables, pluvial precipitation showed a direct but not determinant relationship with population density of T. roseus only in Isla Cacaluta. As a result of the differences observed in the three localities we assume that the factors that could determine the population dynamics of T. roseus are: A larger extension of the area in general, and the contribution of sediments by the presence of rivers in the localities, since Isla Cacaluta was the only locality where there was evidence of an important relationship with pluvial precipitation, and this locality undergoes the influence of the rivers Copalita and Coyula, which produce an important increase in sedimentation rates at this community, affecting the entire benthic community during the rainy season. Rev. Biol. Trop. 63 (Suppl. 2): 121-133. Epub 2015 June 01.

Keywords Population parameters, south Pacific, Echinodermata, Echinoidea, pink flower urchin.

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